Radio transmission units of a radio communications system employing simultaneously a plurality of carriers of different frequencies for transmission of signals are known from the state of the art. With the currently employed technology, such radio transmission units have to comprise a plurality of single-carrier transmitters of which each is capable of transmitting only a single modulated carrier at the same time. With future technology, such radio transmission units may comprise instead one or more multicarrier transmitters, each of which is capable of transmitting several modulated carriers simultaneously. The carriers are usually modulated with modulated signals that are to be transmitted.
The power control of the transmission with the different carriers is an important aspect in the employment of signals using different carriers. Therefore, the present power of the signals transmitted by the radio transmission unit has to be known for each of the different carriers in order to enable an efficient power control. The determination of the actual power of the different carriers in the radio transmission unit is difficult, though, if the transmitted signals using different carriers can only be obtained as a combined output signal. In particular for a digital open-loop power control, the corresponding information has to be obtained in the transmitting radio transmission unit itself.
Summing several modulated signals using different carriers leads to an envelope with heavy fluctuations. Based on such an envelope, there is no simple way to detect the power of each carrier separately. A detection would rather have to be based on complex and possibly inaccurate implementations.